1. Field of the Invention
The present invention relates to a serial printer provided with a cutter for the cutting of a continuous form into several individual sheets.
2. Description of the Prior Art
It is known that continuous forms are generally used in high speed printers for data processing systems to avoid the problems and inconvenience connected with the loading and the feeding of single sheets. The forms commonly used consist of a continuous paper web rolled on a feeding drum, or in a continuous paper web provided with side perforations intended for the form feeding; they are fan folded at regular intervals to form a pile. By the use of continuous forms, the inconvenience of time wasted in the manual loading of separated sheets is avoided. Moreover, separate mechanical equipment for picking up and feeding single sheets in sequence is not required.
Once printing has been performed, sheets from the continuous forms are separated by manual tearing of the continuous form. This is performed with the aid of rulers arranged on the printing equipment transversely to the form. In continuous forms having side perforations, such a separating operation is made easier by partial cuts arranged in correspondence to the foldings. It is therefore clear that with this kind of equipment the manual operation inconveniences are avoided only in part. Even if the manual operation consists only in tearing the form, there is still a waste of time. Moreover, the torn edge quality is poor and unacceptable for several types of documents. In addition, the tearing zone must be quite far from and downstream the printing line. This prevents the printing on a broad zone of the continuous form between the tearing line and the printing line, unless the tearing operation is preceded by the printing of such zone (i.e. by the printing, at least in part, of the next single form). This wastes a great quantity of paper.
Recently, to avoid such inconveniences, serial printers equipped with cutters have been put on the market. In some models, the cutter consists of a pair of shears associated with paper locking devices and controlled by suitable levers. Such a solution assures a good cutting quality but avoids only in part the other disadvantages. In other printers, particularly of the serial type, a cutting roll has been mounted on the printing carriage or on an additional carriage sliding in parallel to the previous one. The cutter must be kept away from a fixed countercutter, transversal to the printing form and parallel to the printing line, by means of a suitable command. In this type of printer, the carriage movement is used to move the cutting roll and to perform the cutting of the continuous form. Examples of printers provided with cutting rolls are described in U.S. Pat. No. 4,234,261 issued on Nov. 18, 1980 and in French patent application No. 2,307,658 published Dec. 8, 1978. Such printers provide for a good cutting quality but they cause other problems in the loading of the continuous form due to the presence in the printer of a form pressing rule extending along the whole cutting line; the need of multiple form feeding equipments, one permanently engaged with the continuous form and the other one for moving and positioning the sheet cut from the form; structural problems which hamper visibility of the printing support; and fabrication complications in urging the continuous forms against the counter cutter during the cutting operation.